Q. What Bloomberg formula can I use to change financial figures of different companies to a common currency for analysis?

You can use the field for currency override, "eqy_fund_crncy" in the Bloomberg formula to change the financial figures to a common currency.

If you want the EBIT of Singapore Airlines to be in USD, you can use this formula:

=BDP("SIA Sp Equity","EBIT","eqy_fund_crncy","USD")